The present invention relates to the general field of determining a surface property of one or more solids. More specifically, the present invention relates to monitoring the effect of desorption on the emission, absorption, or alteration of radiation by the material to determine the surface property.
Many methods have historically been used to evaluate solids and determine their characteristics. For example, U.S. Pat. No. 5,408,864 B1 teaches a method of analyzing the characteristics of an adsorbent using a sample chamber of known volume and known temperature. An adsorptive gas is introduced and the pressure is measured. The quantity of gas adsorbed by the adsorbent at the measured pressure is determined. A relative pressure in the sample chamber and the quantity of adsorptive gas adsorbed by the adsorbent at the relative pressure is correlated. This method is a super atmospheric sub-critical temperature method for determining the amount of a gas adsorbed or desorbed by a solid in a manner such that the corresponding adsorption and desorption isotherms can be constructed. Characteristics such as surface area, pore size distribution, and pore volume can then be determined. Also, thermal effects of a compound being adsorbed on an adsorbent have been used in U.S. Pat. No. 2,826,908 B1 to help identify compounds present in a gas stream.
U.S. Pat. No. 4,566,326 B1 teaches an automatic adsorption and desorption analyzer for independently performing analyses on a plurality of powder samples. A manifold is connected through a plurality of independently operated valves to a corresponding plurality of sample cells. A pressure transducer measures the manifold pressure and a plurality of pressure transducers are respectively coupled to the sample cells to independently measure the pressure at each of the sample cells. The system measures the volume of gas adsorbed or desorbed by each of the samples that is required to establish specified equilibrium pressures at the sample cells to thereby provide pressure-volume points which can be used to prepare adsorption or desorption isotherms or BET curves. U.S. Pat. No. 5,360,743 B1 improves the teachings above by accounting for the void volume, the adsorption of the sample cell walls, and correcting for non-ideal gas behavior.
WO 99/34206 teaches a method for combinatorial material development where the reaction heat generated by chemical or physical processes in materials of combinatorial libraries are made visible by means of differential thermal images of an infrared camera.
U.S. Pat. No. 3,850,040 B1 teaches a gaseous sorption analysis apparatus and method for the measurement at cryogenic temperatures of factors such as surface area, adsorption isotherms and desorption isotherms. The system determines the dead space within a sample container and then adds to the evacuated container in an initial dose of an operating gas such as nitrogen which is equal to the known dead space and other constant volumetric factors plus an additional increment of gas corresponding to a first estimated amount of gas to be adsorbed by the sample. The amount of gas actually adsorbed by the sample is determined and this amount is used to determine the incremental amount of gas to be included in a second dose of gas supplied to the sample for adsorption. Subsequent doses of gas are applied to the sample as required to bring the total amount of gas adsorption up to a level which is a predetermined fraction of the gas saturation pressure of the sample at a fixed temperature. The foregoing steps are repeated a plurality of times to obtain a corresponding plurality of fixed points from which the BET curve is determined for a particular sample.
Infrared thermography has been used to detect and measure catalytic activity in combinatorial libraries of materials. See Holzwarth, A.; Schmidt, H.; Maier, W. F. Angew. Chem. Int. Ed. 1998, 37, No. 19, 2644-2647. U.S. Pat. No. 6,063,633 B1 teaches a method of simultaneously testing a plurality of catalyst formulations to determine comparative catalytic activity of the formulations in the presence of a given reactant or reactant mixture. The method involves supporting the plurality of catalyst formulations on a support and fixing the formulations on the support. The formulations are contacted with a common stream of the reactant or reactant mixture under reaction conditions. Comparative catalytic activity is detected at each of the formulations through sensing radiation admitted, adsorbed or altered by the respective formulations, reactant or products indicative of catalyst activity using a detector. Infrared spectroscopy and imaging of libraries has also been used in WO 98/15813 to determine thermodynamic characterization relating to the absorbable bulk properties of a material such as volume, enthalpy, heat capacity, free energy, heat of reaction, catalytic activity and thermal conductivity. Jandeleit, B.; Schaefer, D. J.; Powers, T. S.; Turner, H. W.; Weinberg, W. H. Angew. Chem. Int. Ed. 1999, 38, 2494-2532, teaches using infrared thermography to monitor temperature changes that arise from the exothermic catalytic acylation of ethanol.
Marengo, S.; Raimondini, G.; Comotti, P. New Frontiers in Catalysis, Gucci, L. et al Eds.; Proceedings of the 10th International Congress on Catalysis, 19-24 Jul., 1992, Budapest, Hungary Elservier Science 1993 2574-2576 teaches the evaluation of the adsorption properties of catalysts using infrared thermography and comparing thermal effects. The present invention, however, allows surface properties of solids to be determined through monitoring the changes in radiation emitted, absorbed, or altered by the solids upon adsorption or desorption of an adsorbate.
One purpose of the present invention is to provide a method of determining a surface property of each of a plurality of solids by contacting the solids with a fluid, measuring the radiation emitted, absorbed, or altered by the solids during contact with the fluid using a detector, and then determining at least one surface property of the solids from the radiation measurements. The invention is particularly useful in combinatorial applications in order to evaluate a plurality of solids or mixtures of solids to determine at least one surface property of each of the solids.
Another purpose of the invention is to provide a method of determining a surface property of at least one solid during desorption of an adsorbate. In this specific embodiment of the invention, the method involves supporting the plurality of solids on at least one support and contacting the plurality of solids with a fluid for a period of time. The fluid is discontinued, and adsorbed fluid is then desorbed from the plurality of solids while the radiation emitted, absorbed, or altered by the respective solids or mixture of solids is measured using a detector. The desorption may be accomplished by, for example, ramping the temperature or the pressure within the apparatus. This specific embodiment may be applied to a single solid as well as to a plurality of solids.
Another purpose of the invention is a method to quantify the amount of a material adsorbed or desorbed by one or more solids.